Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)		3 Months Ended		12 Months Ended
	Jan. 31, 2018	Apr. 30, 2018	Apr. 30, 2017	Jan. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment	$ 1,500,000			$ 0
Aggregate amortization expense		$ 447,000	$ 355,000
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets		5 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets		15 years